The present invention relates to a method of controlling the engagement of an automatic clutch, particularly, the starting of a vehicle having an automatic clutch, by controlling the clutch and an engine on the vehicle at the time the vehicle is started. More particularly, a method of controlling the starting of a vehicle having an automatic clutch for preventing the racing of the engine when operating the clutch, preventing a vehicle starting response from being lowered, and allowing the vehicle to start without suffering from an engine stop or knocking.
Vehicles with automatic transmissions can easily be operated and have widely been used in recent years. Some vehicles have automatic clutches which comprise, instead of torque converters, friction clutches (dry-type single-disc clutches) controlled by fluid-controlled actuators.
Various methods of controlling the automatic clutch have been proposed to permit the vehicle to start smoothly. According to Japanese Patent Publication No. 50-12648, for example, the condition of engagement of the clutch is gradually varied as the number of r.p.m. of the engine is increased. Japanese Laid-Open Patent Publication No. 52-5117 discloses an automatic clutch control method for varying the speed at which the clutch is engaged according to the number of r.p.m. of the engine.
A vehicle with an automatic clutch can be operated in the same manner as that in which conventional vehicles having automatic transmissions with torque converters can be operated. When starting the vehicle, the driver depresses the accelerator pedal to a certain depth and keeps the accelerator pedal depressed until a desired vehicle speed is achieved.
With the torque converter, the engine is subjected to a load at all times, and hence the rate of rotation will not increase dramatically no matter how the accelerator pedal is depressed. The acceleration torque can be increased since a large toque ratio can be obtained by increasing the number of r.p.m. of the engine to increase the slip ratio of the converter. Therefore, the torque converter is advantageous for the above conventional manner of starting the vehicle.
The automatic clutch comprising the friction clutch is engaged after the rate of rotation of the engine has been increased. Thus, the rate of rotation of the engine is substantially increased when the clutch starts being connected. Since the vehicle is held at rest before the clutch is connected, the engine tends to race or run at a high r.p.m. and thus, the clutch slips to a large extent while it is connected incompletely. Therefore, the clutch wears rapidly and has a reduced service life, and the fuel economy of the vehicle is poor. It takes a certain period of time for the rate of engine rotation to increase after the driver has depressed the accelerator pedal. Because the clutch is controlled by the increasing rate of engine rotation, the starting response of the vehicle is lowered. With the poor starting response, the vehilce is slow to start moving, and the driver is then liable to depress the accelerator pedal to a greater depth, with the result that the clutch will have a shorter service life and the fuel economy will get worse.